Breaking out of a nested loop in bash

Question

How do you break out of a nested loop in bash?

Tried continue and break. break worked. But want to learn more.

for i in 1 2 3; do 
  if [[ $flag -eq 1 ]]; then
    break
  fi
done

How does break actually know the loop is nested? Instead of break, can I use i=4 or something out of range to exit from a loop.

An if statement is not a loop, so there is no nested loop in your example. — dtrckd
– dtrckd, Commented Sep 15, 2019 at 23:34
Like most other languages, bash tracks the lexical scope of all statements. While interpreting the if statement, bash has made a note of the fact that it's part of a loop. That's how the break statement knows what to do. — that other guy
– that other guy, Commented Sep 16, 2019 at 0:43

Joseph Sible-Reinstate Monica · Accepted Answer · 2019-09-15 23:33:33Z

34

Use break followed by a number, to break out of that many levels of nesting. Example:

for i in 1 2 3 4 5; do
    echo
    echo i = $i
    for j in 1 2 3 4 5; do
        echo j = $j
        if [ $j -eq 4 ]; then break; fi
        if [ $j -eq 3 ] && [ $i -eq 4 ]; then break 2; fi
    done
done

Result:

i = 1
j = 1
j = 2
j = 3
j = 4

i = 2
j = 1
j = 2
j = 3
j = 4

i = 3
j = 1
j = 2
j = 3
j = 4

i = 4
j = 1
j = 2
j = 3

answered Sep 15, 2019 at 23:33

Joseph Sible-Reinstate Monica

49k7 gold badges55 silver badges118 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

hithesh Over a year ago

In your example, there are 2 for loops. Do the if loops count for break? The default number for break is 1?

Joseph Sible-Reinstate Monica Over a year ago

@hithesh After someone responds to one of your comments, please don't make changes to it that would change the meaning of the response. Anyway, no, ifs aren't loops, so they don't count, and yes, the default is 1.

Serious Angel Over a year ago

Since the anwer edit queue is full, let's use the comment section. break --help should also state relative information. It also worth to mention that a break will end all specified loop depth immediately. In other words, specified loops won't pass until their block end but stop their execution practically instantly. The behavior of "break" depends on the Bash version (e.g. "break" will cause the subshell to exit if reached it in its parent shell), and more information should be available in "Compatibility" details document: tiswww.case.edu/php/chet/bash/COMPAT

Collectives™ on Stack Overflow

Breaking out of a nested loop in bash

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related